Modern data communication networks are generally star-wired “hub and spoke” topologies, with a centralized hub, and multiple spokes which attach to each end-station, generally a computer or computer peripheral device. The centralized hub typically is responsible for conductivity between the individual devices and the network, and may provide a wide range of additional functionality. For instance, a simple Ethernet repeater is responsible for signal timing and amplitude restoration, basically receiving data from one port and repeating it to all other ports. Data received from two or more ports simultaneously constitutes a collision, causing the repeater to issue a “jam” sequence to all ports. The transmitting end-stations will detect the collision condition and back-off, and reschedule their transmission attempt after a predetermined interval. Repeaters usually operate at the physical layer (Layer 1) of the OSI 7-layer model.
A network switch has added functionality, which may allow multiple simultaneously conversations to exist between its ports. Generally, the switch stores a packet (or a portion of it) for some period of time, while it inspects the contents of the packet, and makes a determination as to which port(s) the packet should be forwarded. The switch forwards packets only to where they are destined. It does not forward frames to all ports, as in the case of a repeater, except in the case where it cannot resolve the frame contents to determine which port (s) should receive the frame. Switches may operate at Layer 2 (MAC layer), in which case they are called bridges, or Layer 3 (the network layer) in which case the switches can be referred to as routers. Bridges and routers initially were software-based, requiring a processor to make the forwarding decision. Network switches are generally hardware-based. Advances in VLSI technology have made it possible to integrate the functionality of a bridge (Layer 2 switch) or router (Layer 3 switch) into silicon.
A result of these integration capabilities has been the dramatic cost reduction of hub, or network infrastructure products. This has occurred to such an extent that star-wire topologies have been able to displace the older, traditional bus-based topologies, such as the original coaxial cable-based Ethernet and Cheapernet, with 10BASE-T and 100BASE-T repeater-based technologies. This initially occurred in the corporate environment, where the additional advantages of the star-wire topologies were of substantial value. For instance, fault isolation and diagnosis can be easier in a point-to-point environment where an individual station can be isolated from the rest of the network. Additionally, the centralized hub function can be a natural place to implement network management, since traffic can be monitored at each port, and statistics gathered to determine the performance of the network. However, simple networks, such as for small offices or even in homes, do not require sophisticated management, because it generally adds significant overall cost to the system and is not very useful because in these environments, a professional network manager is not present.